Particle accelerators and cyclotrons have become the best tools for producing short-lived radionuclides and labelled compounds. The rapid growth of nuclear medicine in the advanced countries has quickly required a wider range of isotopes with favorable medical characteristics: short half-life, decay scheme by .gamma. emission, high activity of carrier-free produced isotopes, all of which are more readily capable of being produced in such devices.
Preparation of such isotopes in an accelerator involves bombarding a target with the beam. It has developed that the production of specific isotopes not only involves the use of specific targets and specific beam energies, but in addition, specific beam dimensions. For example, in certain applications a highly focussed beam is required while in other applications a defocussed beam is desired. A variety of beam cross-section configurations may also be necessary in other situations.
Heretofore, beam configuration in an accelerator has been monitored in several ways. In one arrangement, plates may be inserted to block the beam and thereby obtain a picture of its cross-section. Of necessity this is only a sampling arrangement for use at spaced intervals and does give continuous results. A commercially available device which is used for this purpose employs a thin wire matrix, but this device is generally limited to beam intensities in the 10.sup.-.sup.3 to 10.sup.-.sup.2 microampere range. The preparation of radionuclides for medical application quite often involves beams of much higher intensities. Also, these so-called beam analyzers now available tend to be quite expensive.